I didn't feel ready for my first solo, really. I actually was, but I was scared... But fear helps you perform in mild doses (so I've found). If your instructor thinks you're ready, then you most likely are, especially if you request extra practice (remember that his reputation is on the line, so he's thought it through more than you think).
Funny as this may sound, your instructor is in a better position than you to judge your skills.
It's scary, but you just GOTTA DO IT. My instructor sort of sprang it on me (in a Vigilant, aged 16) and you just gotta get on with it. Don't stare at the right hand seat, read the checks out loud, remember that you know how to do it all because you've been trained, take your time, and keep calm. You may permit yourself a brief self-congratulatory chuckle downwind.
Nobody will be able to wipe the grin off your face for several days afterwards
